The deceleration coefficient of friction between a surface and an object brings the moving object to a stop. This coefficient of friction is the factor that relates the object's mass and the gravitational force to the frictional force that decelerates the body. The object stops once this frictional force has performed work equal to the object's initial kinetic energy. You can therefore calculate the coefficient of friction from the factors contributing to the frictional force, the factors contributing to the kinetic energy and the distance the body travels before it stops.
Multiply the moving object's velocity by itself. If, for instance, a car travels at 20 meters each second -- 20 x 20 = 400.
Divide the result by the distance that the object travels before it stops. If, for instance, it travels 150 meters -- 400 / 150 = 2.667.
Divide this answer by 9.81, which is the acceleration downward due to gravity -- 2.667 / 9.81 = 0.2719.
Multiply the result by 0.5 -- 0.2719 x 0.5 = 0.136. This is the deceleration coefficient of friction.